1. Field of the Invention
This invention relates to a film take-up spool of a camera, and more particularly to a film take-up spool suited for a camera having an automatic film threading mechanism.
2. Description of the Prior Art
There are already commercially available cameras having a mechanism in which a plurality of pawls engageable with the perforations of film are provided on a film take-up spool to permit the film loaded into the camera to be easily twined around the take-up spool and when the spool has been rotated by film take-up means, said pawls engage the perforations to cause the film to twine around the spool. As shown in FIG. 2 of the accompanying drawings, the pitch P of the pawls 1a, 1b, . . . of the spool 1 in the conventional camera of this type is equal to the pitch Po of the perforations 2a, 2b, . . . of film 2 shown in FIG. 1 of the accompanying drawings. Therefore, due to the manufacturing error of the pitch Po of the perforations of the film or the pitch P of the pawls of the spool or to the resilient distortion of the film caused when the pawl 1a engages the perforation 2a, the pitch P of the pawls of the spool becomes shorter than the pitch Po of the perforations and accordingly, as shown in FIG. 2, when the first perforation 2a is engaged with the pawl 1a, the second perforation 2b is not engaged with the pawl 1b but the film 2 rides on the pawl. If the first engagement is broken under the influence of the resiliency of the film when the spool 1 has been further rotated in such state, the film would become disengaged from the spool because the second engagement is not accomplished.